Conventionally, chlorinated polyolefin resins and propylene-based random copolymers modified by using acids such as unsaturated carboxylic acid and anhydride thereof, which have an excellent adhesive property, have been used as binders for poorly adhesive polyolefin substrates such as polypropylene and polyethylene. Also in an automobile industry, the above chlorinated polyolefin resins and the above propylene-based random copolymers modified by using the acids such as unsaturated carboxylic acid and anhydride thereof have been used as the binders (particularly referred to as a primer in the automobile industry) for allowing a poorly adhesive paint to adhere to the polyolefin substrate.
In recent years, a drying (baking) temperature in a paint line of automobile parts has tended to be lowered mainly for the purpose of cost saving and preventing deformation of substrates. Furthermore, solvent-based paints are being replaced to water-based paints in terms of environmental problems. Thus, the chlorinated polyolefin resin and the propylene-based random copolymer modified by using acids such as the unsaturated carboxylic acid and the anhydride thereof are required to turned them into water-based.
To improve this, it has been actively attempted to make polyolefin resins water-based. However, conventional aqueous resin composition of such polyolefin resin has a problem in that a surfactant added upon production is left in films and coating films obtained from the composition, which has reduced water resistance of the film and the coating film.
As a method for improving them, Patent Document 1 (JP 2004-18659 A) discloses that acid-modified chlorinated polyolefin can be dispersed in water by using an ether-based solvent without using an emulsifier. However, after removing the ether-based solvent, stability of the resin dispersed in the water is insufficient.
Thus, a dispersed resin composition having an adhesive property to polyolefin-based substrates, being excellent in stability in water or hydrophilic substances, having water resistance upon being dispersed in water, and being excellent in adhesive property regardless of a temperature condition upon baking, has been required.    Patent Document 1:JP 2004-18659 A